Freely flowing suspensions of pigments and other particles



pasntemaymga a a 2,157,378

oF'FcE- FREELY FLowINc' SUSPENSIONS F PIG- MENTS AND o'rnsa PARTICLES Victor It. Abrams, East Orange, N. J., assignor to Sulfio Corporation of America, a corporation of Georgia No Drawing. Application June 10, 1936, Serial No. 84,589. In Japan October 18, 1935 23 Claims. (Cl. 13458) This invention relates to freely flowing suspenlarge enough to be visible to the naked eye, it is sions of finely divided solid particles in organic evident that particles of colloidal size may likeliquid vehicles, and especially to suspensions of wise be stably suspended in accordance with the particles of greater than colloidal size. A parinvention. Colloidal particles thus suspended ticular object of the present invention is to proare rendered stably suspended not only when in vide freely flowing suspensions of pigments for colloidal state but also in the event of agglomcoating purposes, including inks, paints, enamels eration into articles of greater than colloidal and lacquers, although the invention is not Hm,- size, which is not true of particles in ordinary ited thereto and comprehends other suspensions, colloidal suspensions. such as lubricants and grinding, lapping and pol- The gel particles in the suspension mixture are ishing compounds. elastic in nature and resist deformation and dis- Stable, freely flowing suspensions are proplacement in a manner such that-a small force duced, in accordance with this invention, by diswill merely deflect them without producing con- ,tributing through the desired organic liquid ve tinuous motion, and a force in excess of a mini- 1 hicle finely divided particles of solvated hydromum which depends upon the materials and genated castor oil wax having an elasticgel naconditions is required to produce continued moture. This may be conveniently accomplished, tion of any object present in a mass of the parfor example, by dissolving a small amount of the ticles. The result is that the gel particles, and wax in the vehicle at an elevated temperature other particles present, are prevented from movand then cooling to form a waxy precipitate, ing through the mass, the force. of gravity or 0 which, upon proper manipulation of the mixture, buoyancy on each particle being less than the become broken up into finely divided gel particles minimum force required for continuous motion. distributed throughout the. vehicle, the gel par- In this manner even such dense particles as ticles being substantially in contact. The rethose of finely divided lead can be prevented 5 suiting mixture will be of free-flowing consistfrom settling out, and finely divided air bubbles ency if a suitable small amount of wax has been can be prevented from rising and escaping. used. 1 In order to produce the above effect, the gel The particles to be suspended, when distribparticles must be sufllciently close together so uted through this mixture of vehicle and gel parthat they cannot be merely carried through the ticles, are prevented from moving by the gel parliquid vehicle without influencing each other, 30 ticlcs and thus are maintained indefinitely in a and this minimum requirement may be readily stable state of suspension. In other words, the determined by experiment in any desired, case."

wax is used to effect a mechanical suspension of The wax-vehicle mixture capable of sustaining the particles without converting the mixture into particles in stable suspension may be broadly 5 a semi-solid or nonfiowablestate. characterized as. a mobile discontinuous gelatin- As indicated, the function of the solvated wax ous mass composed of particles of waxy elastic particles (gel particles) is not to increase the vis-' gel substantially in contact with each other and cosity and thereby slow ifiiwn the settling or rishaving the interspaces containing the. liquid veing of the suspended particles, which would rehicle, the particles to be suspended being dis- 40 quire that the mixture be made ,of the consisttributed in or between the gel particles and pre- 40 ency of a cake or paste to secure reasonable stavented from moving thereby. bility as to suspended'particles of greater than The term gelcosity.is used to designate this colloidal size, but is to entrain the suspended property of' mobile discontinuous gelatinous particles and'mechanically prevent movement masses, and the degree of force required to prothereof without rendering the mixture incapable duce continuousmotion without such gel masses. 45

of free flow. The use of the wax in accordance The higher the gelcosity, the greater the force With my invention necessarily somewhat in needed to cause continued motion of a particle creases the viscosity of the mixture, but this is through the gelatinous mass, and hence the incidental, and does not prevent securing susgreater the mass of a particle may be without pension mixtures which may be freely poured the particle settling out.

and P p d- The possession of gelcosity and the relative -While suspensions of solid particles of greater gelcosity of various mobile media may be easily than colloidal or sub-microscopic size constitute determined by using a light metal plate or vane the most important application of my invention, suspended in a vertical plane by a fine wire or which may be applied to suspensions of particles fibre secured to a fixed support. The wire should be surrounded by a fixed tube or sleeve to prevent sway. The vane is placed in the medium to be tested and the latter rotated a certain amount, as by turning the receptacle, whereupon the vane will swing about its axis and then return toward its initial rest position due to the restoring force exerted by the wire. If the medium possesses the property of gelcosity, the 'vane will not return completely, but will come to rest in a. displaced position. The greater the displacement the greater. the force needed to cause continuous movement or flow within the medium and hence the greater the gelcosity. If the mobile mediumis continuous, it can have no gelcosity and the vane will slowly return to the initial position even though the medium is highly viscous; while a medium of high gelcosity will cause a large displacement even though of quite free flowing consistency. In other words, a displacement of the vane, which measures a static equilibrium condition, is a consequence of the gelcosity and not of the viscosity.

This characteristic of mobile discontinuous gelatinous masses is not possessed by mobile continuous gelatinous masses, that is, gelatinous masses in which no discrete -'gel particles exist. In the latter case an infinitely small force will produce flow and no gelcosity will be indicated by the above test, just as in the caseof nongelatinous liquids of high or low viscosity. An example of a mobile continuous gelatinous mass is 'a solutionof raw rubber dissolved in a petroleum oil. This possesses the characteristics of elasticity, stringiness and may have a high viscosity, but an infinitely small forcewill produce flow and hence no gelcosity will be exhibited. A gelatinous mass which has set, forming a solid jelly, is also a continuous gelatinous mass, but of course is not mobile and exhibits the overall,

characteristics of a solid until broken up to form a discontinuous mass, and thus obviously does in amounts of .3%

liquids selected from not possess the characteristics of a mobile discontinuous gelatinous mass containing discrete gel particles.

A representative hydrogenated castor oil wax (produced by hydrogenatlng castor oil to an ex-. tent resulting in ,a hard waxy product), is milkwhite in color, has a specific gravity of about 0.99 at 20 (3., has a melting or solidifying point in the range of about 171-178 FL, an acid number of about 2, a saponification number of about 180, and an iodine number of about 3. v

The term wax is applied to the hydrogenated castor oil in accordance with technical usage, since this product is of waxy appearance and is generically similar to the so-called natural or true'waxes in respect to many properties.

Hydrogenated castor oil wax is relatively insoluble at room temperature and thereabouts in most organic vehicles, and in many cases can be satisfactorily used in amounts of 1% or less (for example, with mineral oils, petroleum ether, petroleum naphtha, linseed oil, Cellosolve, and others); It appears to approximate universality, as it has been found to be satisfactory when used or less with the following organic solvents: mineral oil, fish oil, castor oil,

commonly known oils and Methyl Cellosolve (ethylene glycol monomethyl ether), tricresyl phosphate, turpentine, carbon tetrachloride and carbon disulfide.

Combinations of organic liquids can be used, that is, the liquid vehicle may be comprised of one or more components. Pairs or groups of liquids which may be used individually with a given wax may generallybe used in combination, if miscible with each other, as the vehicle. For example, the following combinations, among others, may be used satisfactorily with hydrogenated castor oil wax: linseed oil and mineral oil, linseed oil and naphtha, linseed oil and turpentine, and soy bean oil and Cellosolve. In this way a thin liquid may be thickened, a thick liquid thinned, and 3 other modifications and combinations made use of in preparing the vehicle, as is well known in the art. I

The invention contemplates the use of hydrogenated castor oil wax for the purpose described, in combination with all types of liquid vehicles and bases employed in making inks, paints, enamels and lacquers, and which generally comprise a mixture of ingredients. Thus the vehicle may contain bodying and binding agents, such as polymerized tung oil, boiled linseed oil, nitrocellulose, ester gum (a resingus ester of glycerine and rosin) and other synthetic resinous materials, and natural resinous or gummy products as shellac and copal, A portion of the wax remains dissolved in the vehicle and functions as a plasticizing agent similar to castor oil (which is used in some paints and lacquers, particularly of. the nitrocellulose type).

In the preparation of lubricants and of grinding and lapping compounds, non-volatile petroleum oil fractions are customarily employed as vehicles, and as little as 1-3% or less of the hydrogenated castor oil wax may be incorporated therewith to obtain stable suspensions of finely divided solid lubricants and abrasives.

The organic liquid vehicles which may be employed in accordance with the invention may be genericallycharacterized as those in which the wax is solvatable or lyophilic, meaning that the liquid is capable of being dissolved in or adsorbed by solid wax particles to render them gelatinous, and in which the wax is relatively-insoluble at normal room temperature (20 C. or 68 F.) and thereabouts.

If the wax is readily dissolved in the liquid at an elevated temperature (as distinguished from melting without dissolving), a mutual compatiperatures, there will be so much wax out of ,solution at lower temperatures that the mixture will not befreely flowing at temperatures to be expected under room conditions.

I prefer to employ liquid vehicles in which an 1 amount of the wax not exceeding about 5% by weight, relative to the vehicle, can be used to produce suspending media which will be freely flowing and possessed of substantial gelcosity Y 3,157,378 throughout at least the temperature range of 10-40 C. (50-104 R), and this standard is met and exceeded by all of the various liquid vehicles heretofore named. For example, a suspension having a petroleum oil vehicle (such as a neutral oil of 28-432 Baum gravity) and containing about. 1% of hydrogenated castor oil wax, will be freely flowing and stable at temperatures up'to about The relative insolubility of hydrogenated castor oil wax in a number of common organic liquid vehicles at room temperature and thereabouts, in which the wax is s'olvatable, isshown by the following table:

Since an essentially mechanical suspension of the pigment or other solid particles occurs in the suspending media prepared in accordance with my invention, all types and kinds of pigment and other solid particles may be suspended in -vehicles in which they are .substantially'insoluble and sufiiciently inert, regardless of chemical composition. Thus the invention may be applied generally to obtain stable suspensions of the various pigments in the various organic vehicles employed in the ink, paint and varnish arts, and to obtain new combinations of pigments and vehicles.

As illustrative of various pigments which may be stably suspended,- mention is made of the following: elements and alloysysuch as carbon black and metallic aluminum and bronzing powders; oxides, 'such as zinc white, burnt umber, cobalt blue and red lead; sulfides, such as cadmium yellow andvermilion; hydrates and hydroxides, such as yellow ochre'and raw umber; carbonates, such as white lead; silicates, such as terre verte; chr0- mates, 'such as the yellow chromates (chromates of barium, strontium, zinc and lead), and chrome red (basic lead chromate); various inorganic salts; organic pigments, such' as Prussian blue,

and the various natural and manufactured lakes,

including the dry colors formed by combining dyes with adsorptive or reactive bases such ,as aluminum hydrate.

Lubricant suspensions may be prepared containing finely divided solid lubricant particles of greater than colloidal size, such as flowers of sulfur andfinely divided selenium, tellurium, talc, slaked lime, white lead, white zinc and cork dust. As further examples of suspensions to which the invention applies, mention is made of grinding, lapping and polishing mixtures containing suspended particles of emery, carborundum, rouge, whiting,'or similar substances.

' The term solid particles, as used herein includes semi-solid or plastic particles, such as particles of natural and synthetic resins,

The actual preparation of freely flowing suspensions and suspending media will now be described in'more detail. essential steps of distributing the wax in the liquid vehicle in the form of finely divided discrete particles and solvating or gelatinizing the particles. These steps may be performed ,concurrently or successively; and if performed successively they may take place in either order, that is, the wax may be finely divided and then solvated or gelled, or may be gelled and then the gel mass finely divided. In any case, the initially formed waxy particles may be further subdivided, or solvated, or both, to secure increased gelcosity, and this is generally desirable.

In ordinary practice, I use the plan of solvat ing or gelling the wax with the vehicle of the final product, the wax being either introduced into the whole amount of the vehicle at once, or being first combined with a portion ofthe vehicle and the remainder then added at an appropriate stage.

' Alternatively, the wax may be gelled with one liquid substance and the gel particles thereafter distributed in another liquid substance. In any case, a concentrated suspension product may be prepared containing more wax than .is needed for stably suspending the pigment or other solid particles, and this concentrate may later be diluted by mixing with the same or a different liquid.

The pigment or othersolid material, in powdered form, may be introduced at any stage of preparation, that is, it may be mixed-with the vehicle before or after the wax is added; and if mixed in after addition of the wax it may. be

added either before or after the wax has been reduced to a subdivided gelled state.

It is generally most convenient to incorporate the wax in the vehicle by dissolving the wax in the vehicle at a temperature suflicient for this purpose, and then cooling the solution, prefera-J bly,but not necessarily, without agitation, to a temperature at which most of the wax insoluble at room temperature comes out of solution. The wax may be dissolved in a portion of the vehicle and-the remainder (which is at room temperature) then added to facilitate cooling. If the wax readily forms a gel with the vehicle, a ge latinous phase will be formed, but in some cases afiocculent wax precipitate will be formed which is only partly solvated at this stage.

The next step has as its object .the subdivision of the undissolved wax material and the sol'v a-- tion of this material (particularly if it is not al.-' ready in a highly solvated condition) to form finely divided elastic gel parti les distributed throughout the vehicle. This is accomplished by subjecting the material to thorough mechanical agitation. The mixture may be agitated by the action of a propeller type stirrer which is sufficiently vigorous, by being pumped and repumped through a mixing type pump, or by being milled in a ball or pebble mill, in a roll mill, or in a colloidal mill.

Pumping treatment may be conveniently performed with a gear pump, for example, having an inlet pipe communicating with the bottom of a tank or other receptacle in which the mixture is placed, and having an outlet pipe discharging above the surface of the mixture in the tank. Increased mechanicalaction on the mixture may be effected by. placing a fine orifice in the discharge pipe line. A spring-loaded check valve serves well, the spring being set so that the fluid mixture pumped therethrough will force the valve disk from its seat to form a ring shaped All methods involve the 1 orifice. The advantage of this type of orifice over an ordinary fixed jet-orifice is that greater v uniformity is obtained and clogging is avoided. When material is deposited on the valve seat and disk, the disk will automatically move away from the seat so as to maintain the orifice and permit the deposited material to be washed away.

It is generally preferable to mix the pigment or other material to be suspended, in powdered form, with the wax-vehicle mixture before the latter is subjected to mechanical treatment, or

- the wax particles and facilitate their subdivision and solution. Grinding of pigment material in the vehicle of the product is often resorted to, and such grinding may be performed following incorporation of wax in accordance with the present invention, the grinding simultaneously subjecting the wax to the desired mechanical action.

Mechanical working of a severe nature is generally required to cause adequate solvation of wax in vehicles of the non-viscous organic solvent type, such as petroleum ether, naphtha, benzene, toluene, turpentine, alcohol, acetone, Cellosolve, carbon tetrachloride, and the like. With respect to incorporation of wax in these vehicles, it is not enough to merely subdivide the wax material, and mechanicalwork is needed to cause the liquid to solvate the solid wax phase so as to obtain elastic gel particles. When viscous oil vehicles are used, the wax will usually gel satisfactorily with the vehicle without agitation, that is, a gel will be formed merely by cooling the initial hot solution of wax' in oil, and a mere stirring will produce a mixture which posseses gelcosity; although'agitation should be used in order to subdivide the gel into fine particles. When a nonviscous vehicle is employed, cooling of the initial solution will generally result in a flocculent wax precipitate and the mixture will not exhibit substantial gelcosity upon mere stirring, severe mechanical working being needed to cause liquid to dissolve in or be adsorbed by the wax particles.

A small amount of a wetting agent may be added to facilitate subdivision of the wax or gel' particles during mechanical working. Subdivision of the particles produces an increase in the total surface area of the particles, resulting in an increase in the interfacial or surface energy of the particle system. The greater the magnitude of this energy the greater the'resistance to further subdivision, and the greater the tendency of the particles to agglomerate in .order to decrease the surface area. and surface energy. Under any given working conditions, for example with a particular pumping set up, the available kinetic energy acting on the individual particles is able to reduce the particle size to a more or less definite value only, and no smaller, the energy required for further subdivision being greater than that available. By using a wetting agent, which is adsorbed by the particles, the surface energy per unit of surface area is made lower than it would be otherwise, and hence a greater subdivision and smaller particle size will be produced. Sulphonated castor oil (Turkey Red oil) is an example of a slitable wetting agent and is effective when added to the wax vehicle mixture in amounts of a fraction of one percent. The wetting agent will also act as an agglomeration inhibitor for the wax particles, and may serve the same functions with respect to the pigment or other suspended particles. Other examples of suitable wetting agents are those sold under the trade-names of Erkalin and Avirol". The smaller the size of the gel particles, the greater the suspending power (gelcosity) of the medium, and hence the smaller the amount of wax needed.

Unless suflicient gel material is present to exist in equilibrium with the liquid phase, a serum layer will form even without the presence of pigment or other suspended solid particles in the gelatinous mass. This may be caused by an insuflicient concentration of gel particles, due to insuflicient wax having been incorporated, resulting in a settling of the gel particles until in substantial contact, the mass of gel particles being surmounted by a serum layer of the liquid. If

the wax particles are of lower specific gravity pression of a mass of gel particles, with the result,

that a portion of the liquid present in and between the gel particles may be squeezed out and rise to the surface as a serum layer This may be avoided by employing a sufllcient amount of wax, but the formation of a serum layer is not necessarily detrimental. That is, the formation of a serum layer does not mean that the pigment or other particles are not stably entrained and suspended in the mass of gel particles, but it indicates that an excess of liquid is present. There is no settling of the pigment or other particles to a cake or compact layer on the bottom of the receptacles, as the pigment or other partices will be stably'suspended in the mass of gel particles become entrained during extended pumping or other mechanical agitation of the suspension during preparation. Such dispersed air globules of small size will be held within the gelatinous mass and will be mechanically prevented from rising and escaping Just as the solid suspended particles are prevented from settling, the force of buoyancy on the air particles being insufllcient to produce movement, owing to the gelcosity effect. The buoyant force of the air bubbles tends to offset the downward drag of the suspended solid particles and reduces the compression exerted by the latter, thus reducing the tendency to form a serum layer. This effect may be further increased, to minimize any serum layer, by so conducting the agitation of the mixture as to favor the entrainment o1- air. For exdescribed, in which the mixture is discharged from the circulating pump in a stream onto the surface of the main body, will cause splashing favoring the entrainment of air, and the pumpin pensions such as inks/and paints, in accordance with this invention, results in products having improved tintorial value, and a smaller percentage of pigment can be used.

The presence of the wax gel particles has a still further advantage in the case of inks used in intaglio or gravure printing. In such printa ing, the ink is applied over the whole printing plate and the surplus then wiped ofi with a doctor blade. The gel particles exert a lubricating action which substantially reducesthe wear on the printing plate and on the doctor blade. This advantage is particularly important with respect to large runs on rotarypresses. The steel doctor blade bears against an etched copper cylinder, causing the pigment in the ink to exert a marked grinding effect and substantial wear is produced in this way, both on the cylinder and on the blade. Reduction of wear, owing to the lubricating action of the gel particles, not only increases the life of the doctor blade, but of vastly more importance, increases the number of copies that can be printed from a cylinder and makes possible the use of fewer cylinders in big runs. When a cylinder becomes worn, it is necessary to stop the press and replace it, and a reduction in the number of such changes not only reduces the cylinder costs but the loss of time and the labor and other costs which arise from each. changeover.

The three'principal types of thin pigmente printers inks are: intaglio or gravure inks; aniline type inks containing pigments to give opacity, for printing on Cellophane and other transparent sheets; and news inks. Employment of the invention in the printers ink art is of particular importance with respect to these three types of In the following Examples specific representative embodiments of the invention are set forth for purposes of illustration.

, Example 1 Printers ink of the intaglio or gravure typemay be prepared having a vehicle composed of a volatile hydrocarbon, such as benzol (for fast drying inks) or VIM. & P. naphtha. (for slow dry- .ing inks), blended with a body and binding smooth uniform product is obtained.

Example 2' Printers inks of the aniline type may be prepared using as the vehicle a mixture of about two parts by weight of ethyl alcohol (95%) and one part of shellac. The vehicle mixture. is heated and about l-2% of hydrogenated castor oil wax 'is dissolved therein. The mixture is cooled and the pigment added (such as carbon black or a dry color) to make about 20-35% by weight. The resultant mixture is then agitated, as by'pumping or milling, until smooth .and uniform.

\ Example 3 prepared having a vehicle comprised of 32, parts by weight of ester gum dissolved in 50 parts of V. M. 8; P. naphtha, in which 1 part of hydrogenated castor oil wax is dissolved by heating together. The mixture is allowed to cool and 17 parts of aluminum paint powder are added, the

.resulting mixture then being thoroughly agitated until asmooth uniform product is obtained.

This paint does not cake in the can and can.

be readily applied with a brush. A feature is that it forms a satin or matte finish when painted on a cold surface and allowed to dry, and a large part of the matte effect is retained even when heat is applied after drying. When painted on a hot surface, full gloss is obtained 'due to the leafing of the aluminum flakes as with an ordinary 'unstabilized aluminum paint.

The following examples illustrate the preparation of sulfur suspensions having great value as cutting. lubricants and for other lubrication purposes under extreme-pressure and/or high temperature conditions. Reference may be made to the patent to V. R. Abrams, No. 1,913,300, issued June 6, 1933, for details as to the lubricating action of sulfur suspensions.

Example 5 Melt and dissolve about 1%% (by weight relative to the final product) of hydrogenated castor oil wax in about 20% of petroleum oil, such as a neutral oil of 28-32 Beaum gravity, heating to, a temperature of 200-250 F. Discontinue the heating and add a further quantity of the oil, amounting to about 60% and having about room I temperature, thereby causing cooling and gelling, Then add about-5% of finely divided sulfur (flowers of sulfur, for example), and thoroughly mix and agitate, preferably by pumping and repumping through a small orifice. Add the remainder of the oil (about 13%%) and thoroughly agitate,

as by pumping through a small orifice, to produce smoothness of texture and a finely divided condition of the gel and sulfur particles,

I Example 6 Melt and dissolve 3% of hydrogenated castor oil wax in 12% of petroleum oil, such as'.

a neutral oil of 28-32 Baum gravity, by stirring heating to 200-250 F. Discontinue the heating This mixture provides a lubricant base in con-- centrated form which the user can dilute with two parts of petroleum oil to secure a freely flowing cutting lubricant containing stably suspended sulfur particles of greater than colloidal size.

A valuable feature resulting from the use of the hydrogenated castor oil wax is that sufiicient gelcosity and suspending power will be present even if the user over-dilutes to the extent of producing :1 dilution, which in this extreme case would mean that only 5% of wax would be present.

Example 7 Melt and dissolve 1% ofhydrogenated castor on wax in about 93%% of petroleum. oil, by

stirring and heating to 200-250 F. Cool by any means to about 120 F. Add about of sulfonated castor oil (as commercial Turkey Red oil) and about 5% of powdered sulfur. Then agitate and pump under pressure through -a small orifice to produce smoothness of texture and a uniform distribution of finely divided gel and sulfur particles.

A freely flowing mixture is obtained in which the sulfur is held in stable suspension, and it is adapted to be used directly as a cutting lubricant.

Thisapplication is in part a continuation of my co-pending application Ser. No. 751,413, filed November 3, 1934, and allowed October v22, 1935.

In the claims the word solvated is used in its usual sense, meaning compounded with a liquid to form a gel-like substance, similar to hydrated particles where water is the liquid.

Having disclosed numerous embodiments of the invention, and having discussed the nature of the invention for the assistance of others, but without any intent to be limited thereby, what I claim is as follows:

1. A: freely flowing pigment'suspension for coating purposes, comprising an organic liquid vehicle; in which hydrognated castor oilwax is lyophilic and relatively insoluble at room temperature and thereabouts, containing finely dividedsolvated hydrogenated castor oil wax particles of an an elastic gel nature, and finely divided pigment particles distributed therethrough tributed therethrough, the mixture thereof containing not more than about 5% of the wax and being freely flowing and possessed of substantial gelocosity throughout the entire temperature range of about l0-40 0., and fine1y divided pigment particles distributed therethrough and stably suspended by said solvated wax particles.

3. A freely flowing pigment suspension for coating purposes comprising a freely flowing oil vehicle, in which hydrogenated castor oil wax is lyophilic and relatively insoluble at room temperature and thereabouts, containing finely divided particles of hydrogenated castor oil wax gelled with the vehicle and finely divided pigment particles distributed therethroug'h in a suspended state, the wax being in amount to stably suspend said pigment particles without preventing free flow.

4. A freely flowing pigment suspension for coating purposes comprising a mineral oil vehicle containingfinely divided pigment particles distributed therethrough, and finely divided gel particles of hydrogenated castor oil wax solvated by the oil distributed therethrough in sufiicient amount to stably suspend said pigment particles without preventing free flow of the mixture.

5. A freely flowing pigmentsuspension for coating purposes comprising a vehicle of the nonviscous organic solvent type in which hydroenated castor oil wax is lyophilic and relatively insoluble at room temperature and thereabouts, containing finely divided pigment particles and finely divided gel particles of hydrogenated castor oil waxi solvated with said liquid distributed therethrough, the wax being in amount to stably suspend said pigment particles without preventing free flow.

6. A freely flowing pigment suspension for coating purposes .comprising a volatile hydrocarbon liquid containing finely divided gel particles of hydrogenated castor oil wax solvated with said liquid and finely divided pigment particles distributed therethrough and suspended by said gel particles, the wax being in amount to stably suspendv said pigment particles without preventing free flow. I

7. A freely flowing pigment suspension for coating purposes comprising an organic liquid vehicle containing a discontinuous gelatinous mass of solvated hydrogenated castor oil wax particles relatively insoluble therein at room tem- 'perature and thereabouts, a wetting agent for the wax particles,. and finely divided pigment particles distributed therethrough and stably suspended.

8. A freely flowing pigment suspension for coating pm'poses comprising an organic liquid vehicle containing a discontinuous gelatinous mass of solvated hydrogenated castor oil wax particles relatively insoluble therein at room temperature and thereabouts, a small amount of sulfonated castor oil serving as a wetting agent for the wax particles, and finely divided pigment particles distributed therethrough and stably suspended.

9. A freely flowing suspension comprising an organic liquid vehicle, in which hydrogenated castor oil wax is lyophilic and relatively insoluble at room temperature and thereabouts, containing finely divided solvated hydrogenated castor oil wax particles of an elastic gel nature, and finely divided solid particles distributed therethrough and suspended by said solvated wax particles, the wax being in amount suflicient to stably suspend said solid particles without preventing free flow at room temperature and thereabouts.

10. A freely flowing suspension comprising an organic liquid vehicle in which not more than 5% by weight of hydrogenated castor oil wax isin-which said wax is lyophilic, containing finely divided solvated hydrogenated, castor oil wax particles distributed therethrough, the mixture thereof containing not more than about of the wax and being freely flowing and possessed of substantial gelcosity throughout the entire temperature range of about -40 C., and finely divided solid particles distributed therethrough and stably suspended by said solvated wax particles.

11. A freely flowing suspension comprising a freely flowing oil vehicle, in which hydrogenated castor oil wax is lyophilio and relatively insoluble at room temperature and thereabouts, contain-- ing finely divided particles of hydrogenated castor oil wax gelled with the vehicle and finely divided solid particles distributed therethrough in ,a suspended state, the wax being in amount to stably suspend said solid particles without preventing free flow.

12. A freely flowing suspensioncomprising a mineral oil vehicle containing finely divided solid 'particles distributed therethrough, and finely divided gel particles of hydrogenated castor oil wax solvated by the oil distributed therethrough in sufficient amount to stably suspend said solid particles without preventing "free fiow of the mixture.

13. A freely flowing suspension comprising a vehicle of the non-viscous organic solvent type in which hydrogenated castor oil wax-is lyophilic and relatively insoluble at room temperature and thereabouts, containing finely divided solid particles and finely divided gel particles of hydrogenated castor oil wax distributed therethrough, the wax solvated with said solvent vehicle being in amount to stably suspend said solid particles without preventing free flow.

14. A freely flowing suspension comprising a volatile hydrocarbon liquid containing finely divided gel particles of hydrogenated castor oil Wax solvated with said liquid and finely divided solid particles distributed therethrough and suspended by said gel particles, the wax being in amount to stably suspend said solid particles without preventing free flow.

15. A freely flowing suspension comprising an organic liquid vehicle containing a discontinuous gelatinous mass of solvated hydrogenated castor oil wax particles relatively insoluble therein at room temperature and thereabouts, a'wetting agent for the wax particles, and finely divided solid particles distributed therethrough and stably suspended.

16, A freely flowing suspension comprising an organic liquid vehicle containing a discontinuous gelatinous mass of solvated hydrogenatedcastor oil wax particles relatively insoluble therein at room temperature and" thereabouts, a small amount of sulfonated castor oil serving as a wetting agent for the wax particles, and finely 'divided solid particles distributed stherethrough and stably suspended. V I

17. A composition of matter comprising in combination a freely flowing suspending medium composed of a mineral oil vehicle containing finely divided gel particlesof hydrogenated cas-. tor oil wax and mineral oil in sufficient amount to possess suspending power but not to prevent free flow, and finely divided solid particles of greater than colloidal size, other than said gel particles, distributed therethrough in an amount to be stably suspended by said gel particles, said solid particles being substantially insoluble in the mixture.

18. A composition of matter comprising in combination a freely flowing. suspending medium composed of a mineral oil gelled with a small amount of hydrogenated castor oil wax, constituting a mobile discontinuous gel containing finely divided gel particles and having the property of gelcosity, solid particles of greater than colloidal size in addition to said gel particles distributed therethrough in an amount to be stably suspended, said solid particles being of a kind substantially insoluble in the mixture, and an agent to inhibit agglomeration of the gel particles.

19. A composition of matter comprising in combination a mobile discontinuous gelatinous mass containing finely divided particles of elastic gel composed of mineral oil and a small amount of hydrogenated castor oil wax, said particles being volatile organic liquid vehicle and pigment particles and containing finely divided solvated hydrogenated castor oil wax particles relatively insoluble in said suspension at room temperaturein amount sufiicient to form a discontinuous gel wherein said pigment particlesarestably suspended.

21. A fiowable non-settling pigment suspension for coating purposes comprising printers ink of the news type including a non-volatile organic liquid vehicle and pigment particles and containing finely divided solvated hydrogenated castor oil .wax particles relatively insoluble therein at room temperature in sufficient amount to form a discontinuous gel wherein said pigment particles are stably suspended.

22. A fiowable non-settling pigment suspension for coating purposes comprising aluminum paint including an organic liquid vehicle and aluminum powder and containing finely divided solvated hydrogenated castor oil wax particles relatively insoluble therein at room temperature in sufficient amount to form a discontinuous gel wherein said pigment particles are stably suspended.

23. A'flowable non-settling pigmentsuspension for coating purposes comprising an organic liqpid vehicle mixed with a substance of the class consisting of natural and synthetic resins and pigment particles and containing finely divided solvated hydrogenated castor oil wax particles relatively insoluble in said suspension at room temperature in suflicient amount to form a-discontinuous gel wherein said pigment particles are stably suspended.

' VICTOR R. ABRAMS. 

